Bobbin-wound coil with connected and anchored coil leads

ABSTRACT

A BOBBIN-WOUND ELECTRICAL COIL HAS ITS ENDS SOLDERED TO CONDUCTOR ENDS OF INSULATED COIL LEADS WITHIN THE PERIPHERAL CONFINES OF THE BOBBIN, WITH THE LEADS EXTENDING WITH A LOOSE FIT THROUGH HOLES IN ONE OF THE OPPOSITE FLANGES OF THE BOBBIN, AND HAVING NEXT TO THEIR COIL-CONNECTED ENDS ENLARGED COLLAR FORMATIONS ON THEIR INSULATION WHICH LOCK THE LEADS AGAINST RETRACTION FROM THE BOBBIN.

9 L. R. BURGHOFF 3,559,135 v BOBBIN-WOUND COIL WITH CONNECTED ANDANCHORED COIL LEADS Filed Nov. 4. 1968 INVENTOR l 01/231? 5111' Z10 BYATT RN United States Patent 3,559,135 BOBBIN-WOUND COIL WITH CONNECTEDAND ANCHORED COIL LEADS Louis R. Burghoif, Delavan, Wis., assignor toThe Bunker- Ramo Corporation, Oak Brook, lll., a corporation of DelawareFiled Nov. 4, 1968, Ser. No. 773,062 Int. Cl. H01f 15/10 US. Cl. 3361924 Claims ABSTRACT OF THE DISCLOSURE A bobbin-wound electrical coil hasits ends soldered to conductor ends of insulated coil leads within theperipheral confines of the bobbin, with the leads extending with a loosefit through holes in one of the opposite flanges of the bobbin, andhaving next to their coil-connected ends enlarged collar formations ontheir insulation which lock the leads against retraction from thebobbin.

This invention relates to electrical coils in general, and tobobbin-wound coils with thereon anchored coil leads and'a method ofanchoring them thereon in particular.

Coil leads, which are usually solder-connected with the ends ofbobbin-wound coils, are anchored to the bobbins in various ways of whichthe more common ones involve string ties, fabric and adhesive tapes, orstaples and cards, for securing the connected leads against separationfrom the coils in installing or otherwise handling the latter. Whilethese lead anchors on coils are generally satisfactory, they areobjectionable in a few, but important, respects. Thus, the formation ofthese lead anchors is a tedious and time-consuming task involvingconsiderable cost in any event. Furthermore, these lead anchors usuallyadd considerable bulk to the coils and frequently cause local bulging ofthe coils beyond the bobbin peripheries with ensuing likely interferencein mounting the coils in crowded spaces. Moreover, lead anchorsinvolving staples and cards are liable to cause coil failure by cuttingthrough the insulation on leads either on application of the staples oron their subjection to pressure in mounting the coils. Even moreimportant, these lead anchors just barely meet the minimum pull-testrequirements of withstanding a pull of a specified number of pounds fora specified time period.

It is among the objects of the present invention to provide abobbin-wound coil with thereto connected insulated coil leads of whichthe latter are anchored to the bobbin in a manner in which the leadanchors are devoid of any of the objections, and are also in otherrespects superior, to the aforementioned lead anchors on bobbin-Woundcoils.

It is another object of the present invention to provide a bobbin-woundcoil of which the thereto connected coil leads are anchored to thebobbin by positive interlock with the latter of the insulation on thecoil leads near their coil-connected conductor ends, so that any pull onthe coil leads outside the bobbin is wholly taken up by the bobbin andno part thereof is transmitted to the coilconnected lead ends. With thisarrangement, the anchorage of the coil leads to the bobbin isincomparably firmer than the aforementioned different lead anchors, withthe present lead anchorage safely resisting a pull on the leads of anymagnitude short of that at which the interlock will break.

It is a further object of the present invention to provide abobbin-wound coil with thereto connected coil leads in which, for theaforementioned interlock between the bobbin and insulation of the coilleads, there are provided in preferably one of the opposite endflangesof the bobbin between its outer periphery and the wound coil therein twoICC apertures through which the coil leads extend with a loose fit tothe outside of the bobbin, and the insulation of each coil lead haswithin the peripheral confines of the bobbin an enlarged collar-likeformation which on outward pull on the lead is firmly drawn against theinner face of the associated endflange of the bobbin so that the entirepull force is taken up by this endflange. While with this arrangementthe anchorage of each coil lead to the bobbin is particularly firm,there is this further advantage that each coil lead may advantageouslybe assembled with the bobbin and anchored thereto before being connectedwith the respective coil end, whereby the task of making the connectionis considerably facilitated and not even an accidental pull on the leadwill interfere with this task or adversely affect the connection.Moreover, each anchored lead has some freedom of sliding movement intothe bobbin for any give to permit its quickest, easiest and most secure,connection with the respective coil lead outside of the narrow bobbinconfines. Further, with each lead anchor being entirely within theconfines of the bobbin, it is entirely natural as well as advantageousto also confine the connection of each lead with its coil end within thebobbin and still afford therewithin ample space for a usual protectiveouter wrapping on the coil.

Another object of the present invention is to provide a bobbin-woundcoil with thereto connected coil leads of which the aforementionedcollar-like formations on the insulation of the coil leads arepreferably and advantageously integral parts of the insulation.

A further object of the present invention is to devise a method offorming the aforementioned integral collarlike formation on preferablythermoplastic insulation of each coil lead, according to which anendlength of the insulation next to an exposed conductor end of the leadis heated to a semiplastic state, and while in such semiplastic state isby a tool upset around the conductor therein, with ensuing backwarddisplacement of such insulation on the conductor and its simultaneousoutward spread into the collar-like formation.

It is another object of the present invention to provide in theaforementioned method for heating an endlength of the insulation next toan exposed conductor end of the lead, by advantageously applying heat toits exposed conductor end for transfer of this applied heat by thelatter to the nearby insulation, and then upsetting the thus heatedinsulation with a cold tool. With this mode of heating the insulation tosemiplasticity, the insulation may be kept fully exposed and, hence,cannot stick to anything, and with the upsetting tool being cold, thisinsulation will readily be upset thereby with negligible force and willquickly set without having a chance to stick to the tool.

It is still another object of the present invention to further providein the aforementioned method for assembling the coil leads with thebobbin by passing them with their other ends from the inside of thebobbin through the apertures in one of the endflanges thereof to theoutside, and then connecting their exposed conductor ends next to theirupset insulation ends to the respective coil ends, preferably bybringing these conductor and coil ends outside the narrow confines ofthe bobbin and there quickly intertwisting the respective ends and thensimply dipping them in a solder bath Without any impediment from thebobbin. With this enhanced method, the task of electrically connectingthe coil ends and ends of the respective coil leads is of theaforementioned considerable facility, and these connected coil and leadends may subsequently be readily stowed, or simply turned, into theconfines of the bobbin for optimum protection therein.

Further objects and advantages will appear to those skilled in the artfrom the following, considered in conjunction With the accompanyingdrawings.

In the accompanying drawings, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

FIG. 1 is an end view of a bobbin-wound coil with connected and anchoredcoil leads according to the invention;

FIGS. 2 and 3 are side and top views of the same coil;

FIG. 4 is a view of one of the coil leads of the bobbinwound coil;

FIGS. 5, 6 and 7 show progressive steps in forming the coil lead of FIG.4 with an anchor formation;

FIGS. 8 and 8A show progressive steps in electrically connecting thecoil leads with the ends of the bobbinwound coil; and

FIG. 9 is an end view of a bobbin-wound coil with connected and anchoredcoil leads according to a modification of the invention.

Referring to the drawings, and more particularly to FIGS. 1 to 3thereof, the reference numeral 10 designates a bobbin-wound coil ofwhich the bobbin 12 is of any suitable insulating material, such asplastic, for example, and has opposite end flanges 14 that flank thewound coil 16. The coil 16 of bare conductive wire is wound directly inthe bobbin 12 in conventional manner, with the opposite wire ends 18 ofthe coil 16 extending beyond the outer coil periphery. As usual, thecoil 16 is held against unraveling by a few turns of adhesive tape 1 orthe like on its outer periphery, with the coil ends 18 being passedabove the tape for connection with coil leads 20.

Each of the coil leads 20 has an electrical conductor 22 with aninsulation coating 24, with opposite ends 26 and 28 of the conductorbeing stripped of insulation for electrical connections. In thisinstance, the bare conductor ends 26 of the coil leads 20 areelectrically connected with the respective coil ends 18 as at 30.

Each coil lead 20 is also anchored to the bobbin .12 to prevent itsdisconnection from the respective coil end 18 on subjection of the leadto pull or other forces. To this end, and in accordance with animportant aspect of the present invention, each coil lead 20 is with itsinsulation 24 interlocked with the bobbin 12 against removal therefromthat would break its connection with the coil 16. In this connection,the opposite flanges 14 of the bobbin are, as usual, of larger outsidediameter than the coil 16, so that these flanges have peripheral margins32 which extend beyond the outer coil periphery. There are provided inthe flange margins 32, and in this instance only in one flange margin32, two spaced identical apertures 34 through which the coil leads 20extend with a relatively loose fit of their insulation 24 therein, withthe greater lengths of the coil leads projecting outside the bobbin 12for connection with their ends 28 in an intended circuit. The coil leads20 have, at the ends of the insulation coatings 24 next to theircoil-connected ends 26 and within the peripheral bobbin confines,outward collar formations 36 which by abutment against the inner face 38of the flange margin 14' lock these coil leads against outward removalfrom the bobbin. Thus, with these collar formations 36 on, andcoil-connected ends 26 of, the coil leads 20 being within the peripheralconfines of the bobbin and also preferably held therein by a few turnsof adhesive tape or the like thereover (not shown), the only way thecoil lead connections with the coil could be torn apart would be pullforces on the coil leads outside the bobbin, but such pull forces ofmost any magnitudes are wholly taken up by the described anchors of thecoil leads on the bobbin and are in no ways transmitted to the coil leadconnections with the coil.

The insulation 24 of each coil lead 20 is of plastic, and preferablythermoplastic, which is extruded in usual manner onto the conductor 22.The collars 36 on the insulation coatings 24 of the coil leads 20 areformed as integral parts of these coatings in accordance with a methodwhich is part of the present invention. To begin with, the collars 36are formed on the insulation coatcal ings 24 of the coil leads 20preferably before the latter are assembled with the bobbin 12. Accordingto the method just mentioned, the end of the insulation coating 24 nextto the bare conductor end 26 of each coil lead is in any suitable mannerheated to semiplasticity, whereupon this end part of the coating, whilestill in a semiplastic state, is upset, with ensuing strip-back ofinsulation on the conductor and simultaneous spread of the same into thecollar formation 36. Preferably and advantageously, this end part of thecoating of each coil lead 20 is heated by heating the nearby bareconductor end 26 which transrnits the applied heat to the coating. Thismay be achieved by contacting the bare conductor end 26 with anelectrically or otherwise heated element 42 (FIG. 5), from which it willbe retracted after a given short time interval when the end part 40 ofthe coating is known to be in proper semiplastic state for itsimmediately following formation into the collar 36 by upsetting.

For upsetting the semiplastic end part 40 of the coating of each coillead 20, recourse may be had to a tool 44 having a bore 46 and acounterbore or recess 48 (FIGS. 6 and 7), of which the bore 46 is of adiameter to receive the conductor end 26 of the coil lead with arelatively loose fit, while the recess 48 is of a diameter which may bethe same as, but preferably is slightly larger than, the diameter of thecollar 36 to-be-for-med. Thus, while the end part 40 of the insulationcoating 24 on the coil lead 20 is still in a semiplastic state, the coillead is with its conductor end 26 passed into the tool 44 and into thebore 46 therein (FIG. 6), and is then quickly thrust all the way intothe tool (FIG. 7), whereby the ring-like shoulder 50 formed by thebottom of the recess 48 upsets the end part 40 of the coating which, inconsequence, is formed into the collar 36. While the described preferredheating to semiplasticity of the end part 40 of the coating 24 via theconductor end 26 (FIG. 5) is advantageous for several reasons, includingno contact of the semiplastic insulation with anything to which it mightstick, non-sticking of this semiplastic insulation also prevails in theupsetting operation in that the contact area between this insulation andthe upsetting shoulder 50 is quite small, and the tool 44 is used in acold state in which it helps to expedite setting of the insulation overits small contact area therewith. Moreover, the described thrust of thesemiplastic end part of the insulation against the upsetting shoulder 50is preferably quite brief and, hence, non-conducive ot sticking of theinsulation to this upsetting shoulder.

While the formation of the collar 36 on the insulation coating 24 ofeach coil lead 20 according to the method just described is particularlyeflective where the insulation is of thermoplastic material, the samemethod is also effective to produce an adequate collar-like formation oninsulation which is of vulcanized rubber or rubber-like material. Thus,on heating the latter kind of insulation and upsetting the same whilestill heated, the insulation will undergo sufficient permanentdeformation into a collar-like formation adequate for the purpose ofsecure coil lead anchorage to the bobbin.

Preferably and advantageously, the bobbin-Wound coil 10 and coil leads20 are assembled according to a method which is also part of the presentinvention. Thus, after first forming the collars 36 on the insulationcoatings of the separate coil leads 20 as described, these coil leadsare next anchored to the bobbin 12 by simply passing them,

with their conductor ends 28 leading, through the respective apertures34 in the flange margin 14' of the bobbin from inside the latter to theoutside thereof. Next, the coil ends 18, which as already mentioned areleft sufiiciently long for their outward extension beyond the peripheralbobbin confines, are drawn out from the bobbin confines if they are notalready so extended, and the conductor ends 26 of the anchored coilleads are similarly extended outwardly from the peripheral bobbinconfines where each conductor end 26 is initially connected with a coilend 18 by simply ,intertwisting them at 52 Without any impediment fromthe bobbin (see also FIG. 8), whereupon the thus initially connectedpairs of conductor and coil ends 26 and 18 are dipped in a solder bath b(FIG. 8A) to finish their connection. These pairs of finishconnectedconductor and coil ends 26 and 18 are then stowed back into theperipheral confines of the bobbin preferably into close proximity to thetape-covered coil 16 (FIG. 2) for application of a final outer tapewrapper thereover (not shown). Stow-back of the connected conductor andcoil ends into the peripheral bobbin confines is achieved in simplemanner by turning the coil leads 20 on the outside of the bobbin.Further, the collars 36 on the insulation of the coil leads 20, by whichthe latter are anchored to the bobbin 12, afford some freedom of inwardmotion of the coil leads in the bobbin and, hence, temporary outwardextension of the conductor ends 26 from the bobbin to any extentmatching that of the coil ends 18 for their intertwisting (FIG. 8) withthe least impediment from the bobbin 12. Of course, if for theconnection of the conductor ends 26 with the coil ends 18 the anchoredcoil leads 20 are moved with their collars 36 slightly inwardly and awayfrom the flange margin 14 of the bobbin as in FIG. 8, for example, thecoil leads are subsequently preferably pulled back with their collars 36into abutment with the flange margin 14' before applying thebeforementioned final outer tape wrapper.

Reference is now had to FIG. 9 which shows a modified bobbin-wound coil10a with attached and anchored coil leads a. In this modified coilconstruction the flange margin 32a of the "bobbin 12a is devoid ofapertures through which the coil leads extend, and is instead providedwith two radial slots 60 in its outer peripery into which the coil leads20a are conveniently inserted laterally. Adhesive tape or the like p maythen be applied to the bobbin to close the open ends of the slots 60 andlock the coil leads 20a against lateral removal therefrom.

What is claimed is:

1. Anchorage of a pair of coil leads on a bobbin with a wound-in coilhaving outer exposed ends, with the coil leads being insulation-coatedelectrical conductors having insulation-bare ends connected with saidcoil leads, respectively, which comprises opposite coil-flanking flangeson the bobbin each with a peripheral margin extending outwardly beyondsaid coil, and two apertures in said flange margins through which saidleads extend with sliding freedom; and a collar on each coil lead formedby a cross-sectionally enlarged part of the insulation thereof andlocated between said flange margins, with the collar on each coil leadbeing of larger cross-sectional dimension than the aperture in theassociated flange margin through which the lead extends, whereby eachcollar will have some play to and from the associated flange margin andwill be held in forced abutment therewith by the respective lead whenthe latter is strained for retraction from the bobbin outwardly throughthe aperture through which it extends.

2. Coil lead anchorage as .in claim 1, in which said collar-likeformations are provided on the ends of the insulation of said coil leadsnext to their respective coilconnected ends.

3. Coil lead anchorage as in claim 1, in which each of said apertures isformed by a radial slot in the outer periphery of its flange.

4. Coil lead anchorage as in claim 3, in which each of said slots is atthe outer periphery of its flange closed by a crossing tape secured tosaid flange.

References Cited UNITED STATES PATENTS 797,049 8/1905 De Kaiser 339-1062,223,153 11/1940 Seifer 339106 2,243,553 5/1941 DEntremont 3361922,869,089 1/1959 Hampel 336-192 2,999,962 9/1961 Wahl 336l92X 3,259,8647/1966 MarZOIf 336l92 3,395,374 7/1968 Morrison et al 336192X 3,461,4148/1969 Fearon 336192 FOREIGN PATENTS 466,824 6/1937 Great Britain336-192 402,105 11/1965 Switzerland 174l35 ELLIOT A. GOLDBERG, PrimaryExaminer US. Cl. X.R.

